1. Field of the Invention
The present invention relates to an index apparatus for indexing to a predetermined operative position each of a plurality of tools carried on a tool support of a machine tool.
2. Description of the Prior Art
A conventional index apparatus is provided with a pair of gear couplings for indexing a tool support carrying a plurality of tools. In such an index apparatus, the tool support has to be lifted before the indexing operation. For this reason, a vertical shaft carrying the tool support is slidably and rotatably supported in a base. A gear member is rotatably but non-slidably mounted on the support shaft and is provided with a threaded portion threadedly engaged with the base. A sleeve member having a rack engaging with the gear member is moved axially to lift the tool support for the indexing operation. However, when the tool support carries heavy tools, the sleeve member may be moved axially during the indexing operation to thereby move the tool support downward, which results in inaccurate indexing of the tool support.